1. Technical Field
The present invention relates to an actuator control device for a dual-control actuator which adjusts the angles of variable stator vanes used in a fan, a compressor, a turbine, or the like of a jet engine.
2. Description of the Related Art
A fan, a compressor, or a turbine of a jet engine is provided with variable stator vanes 101. As shown in FIG. 4, the variable stator vanes 101 are configured such that the angles thereof can be changed in accordance with load status. To change the angles of the variable stator vanes 101, a first (master-side) hydraulic cylinder 104 as a first actuator and a second (slave-side) hydraulic cylinder 105 as a second actuator are used. The first hydraulic cylinder 104 and the second hydraulic cylinder 105 are connected to a link 103 to face each other across a rotation axis 102, and give the link 103 turning forces in the same direction. It should be noted that in FIG. 4, 106 denotes a piston of the hydraulic cylinder 104, and 107 denotes a piston of the hydraulic cylinder 105. One end of a bell crank 108 is connected to a tip of the piston 106, and one end of a bell crank 109 is connected to a tip of the piston 107. Other ends of the bell cranks 108 and 109 are connected to the link 103. The bell cranks 108 and 109 are rotatably supported by fixing members (not shown). Accordingly, when the bell cranks 108 and 109 rotate in conjunction with the ejection and retraction of the pistons 106 and 107, the link 103 rotates about the central axis 102. As a result, the angles of rotation of the variable stator vanes 101 are adjusted. It should be noted that arrows in FIG. 4 indicate the movement of the bell cranks 108 and 109, the link 103, and the variable stator vanes 101 for the case where the pistons 106 and 107 are displaced in directions (directions of extension) in which the pistons 106 and 107 are pushed out.
FIG. 5 shows a modeled link mechanism for the variable stator vanes 101. By modeling, the link 103 is represented as a rod-shaped coaxial synchronous link. In this model, a central portion of the link 103 is pivotally supported about the rotation axis 102, the piston 106 of the first hydraulic cylinder 104 is connected to one end of the link 103, and the piston 107 of the second hydraulic cylinder 105 is connected to other end of the link 103 in an opposite direction. When the pistons 106 and 107 are simultaneously pushed out or pulled back, a forward or reverse turning force is applied to the link 103. It should be noted that arrows in FIG. 5 indicate the movement of the link 103 for the case where the pistons 106 and 107 are displaced in directions (directions of extension) in which the pistons 106 and 107 are pushed out.
FIG. 6 is a block diagram of a conventional actuator control device for controlling the angle of rotation of a modeled synchronous link 2. This conventional actuator control device employs a one-servo valve active-standby configuration. In this configuration, fluid (working fluid) for driving each hydraulic cylinder is simultaneously supplied to or discharged from the hydraulic cylinders 4 and 5 as actuators through a single servo valve 8. Psup denotes supply paths of fluid to the servo valve 8, Pret denotes return paths of fluid, Qh denotes flow paths of fluid to respective piston head chambers Ph of the hydraulic cylinders 4 and 5, and Qr denotes flow paths of fluid to respective piston rod chambers Pr of the hydraulic cylinders 4 and 5. Displacement sensors F_A and F_B are installed in the pistons 6 and 7 of the hydraulic cylinders 4 and 5, and detect the displacement positions of the pistons 6 and 7 to provide feedback. In FIG. 6, the displacement sensor F_A feeds back a detected displacement value XVSVFB_A indicating the displacement position of the piston 6 of the hydraulic cylinder 4 for driving one end (end A) of the synchronous link 2, and the displacement sensor F_B feeds back a detected displacement value XVSVFB_B indicating the displacement position of the piston 7 of the hydraulic cylinder 5 for driving other end (end B) of the synchronous link 2.
Moreover, in the actuator control device of FIG. 6, the single servo valve 8 drives a spool 9 using dual redundant coils T/M_A and T/M_B of a torque motor to perform supply/return operating mode switching and flow rate adjustment. Further, driving currents passed through the dual redundant coils T/M_A and T/M_B of the servo valve 8 are controlled by a control unit 10. A servo valve driver 15 receives a control current command from the control unit 10, and performs control so that a torque motor driving current may be passed through one of the dual redundant coils T/M_A and T/M_B which has received the command. This causes the torque motor to rotate by a predetermined angle and causes the spool 9 of the servo valve 8 to move by a predetermined amount of travel.
The control unit 10 alternately turns on (close) and off (open) current supply switches SW_A and SW_B in order to select a properly operating one of the two systems in the case where a malfunction occurs in one of the two systems, or in order to alternately the activate system A or the system B at every start-up time even when these systems are properly operating. In the following, for convenience of explanation, a description will be made of feedback control operation for the case where system A is active (ATV) and where system B is standby (STB). Control position target values XVSVREF_A and XVSVREF_B (these are generally common values of independent operations) are inputted to plus-signed terminals of subtractors 11 and 12, and the detected displacement values XVSVFB_A and XVSVFB_B of the displacement sensors F_A and F_B are fed back to minus-signed terminals of the subtractors 11 and 12. Further, the subtractors 11 and 12 perform subtractions on these input quantities, and output difference values as controlled variables. PID controllers 13 and 14 perform PID operations on the difference values outputted from the subtractors 11 and 12, and output calculation results as current command values. The gains of the PID controllers 13 and 14 are K.
As shown in FIG. 6, when system A and system B are respectively set to active and standby, and the current supply switch SW_A and the current supply switch SW_B are respectively on and off, the current command value outputted from the PID controller 13 is inputted to the servo valve driver 15, and the servo valve driver 15 passes a current in accordance with the current command value through the dual redundant coil T/M_A of system A to rotate the torque motor. The spool 9 is driven by the rotation of the torque motor to simultaneously supply fluid to the piston head chambers Ph of the two hydraulic cylinders 4 and 5 and simultaneously collect fluid from the piston rod chambers Pr thereof, or to simultaneously supply fluid to the piston rod chambers Pr of the two hydraulic cylinders 4 and 5 and simultaneously collect fluid from the piston head chambers Ph thereof. Ideally, this causes the pistons 6 and 7 of the two hydraulic cylinders 4 and 5 to be pushed out or pulled back by the same amount of displacement, and this produces driving forces which rotate the synchronous link 2 in a forward direction (counterclockwise direction in FIG. 6) or in a reverse direction (clockwise direction in FIG. 6) by a predetermined angle. This is the feedback control of the synchronous link by a conventional actuator control device employing a one-servo valve active-standby configuration.
Moreover, a conventional actuator control device employing a one-servo valve active-active configuration has also been known. The configuration thereof is shown in FIG. 7. In the actuator control device of FIG. 7, components identical with or similar to those of the conventional actuator control device shown in FIG. 6 are denoted by the same or like reference signs.
In the conventional actuator control device shown in FIG. 7, in the control unit 10, the current supply switches SW_A and SW_B of system A and system B are simultaneously turned on and made active, and a control current is simultaneously passed through the dual redundant coils T/M_A and T/M_B of the torque motor in accordance with results of feedback PID control operations of the PID controllers 13 and 14 to control the servo valve 8. In this configuration, both of outputs of the PID controllers 13 and 14 are valid (both are used). Accordingly, the gains of the PID controllers 13 and 14 are set to K/2 in order to obtain the same control performance as that of the configuration of FIG. 6.
These conventional actuator control devices perform the operation of simultaneously supplying or collecting fluid to/from the piston head chambers Ph and the piston rod chambers Pr through the single servo valve 8 and the flow paths Qh and Qr. It is impossible to perform control so that the pistons 6 and 7 of the hydraulic cylinders 4 and 5 may be moved strictly at the same time by the same distance while generating the same force, due to the individual difference between the hydraulic cylinders 4 and 5, the difference in length between the flow paths Qh and Qr from the single servo valve 8 to the hydraulic cylinders 4 and 5, the individual difference between the flow paths themselves, friction, rattle, and the like of components including the synchronous link 2 and junctions. Accordingly, turning forces acting on two opposite ends of the synchronous link 2 do not strictly match, and may create an imbalance. In that case, there has been a problem that so-called force fighting occurs which applies an excessive force to the synchronous link 2.
As an actuator control device which solves this, an actuator control device employing a two-servo valve active-active configuration such as shown in FIG. 8 has also been known. It should be noted that in the actuator control device of FIG. 8, components identical with or similar to those of the conventional actuator control devices shown in FIGS. 6 and 7 are denoted by the same or like reference signs.
In this configuration shown in FIG. 8, two servo valves 81 and 82 individually drive the two hydraulic cylinders 4 and 5, and turning forces are respectively applied to two opposite ends of the synchronous link 2. These turning forces are simultaneously and individually adjusted in system A and system B by feedback control. Here, positions of the servo valves 81 and 82 are backed up by interchannel communications. Moreover, feedback control in each of system A and system B employs an active-standby configuration. Specifically, when a malfunction occurs in each system, the actuator control device selects a properly operating switch from the current supply switches SW_A1 and SW_A2 of system A, and selects a properly operating switch from the current supply switches SW_B1 and SW_B2 of system B. Moreover, even in a normal case, the actuator control device alternately turns on and off the current supply switches SW_A1 and SW_A2 of system A and alternately turns on and off the current supply switches SW_B1 and SW_B2 of system B at every start-up time. It should be noted that the gains of the PID controllers 13A and 14A of system A and the PID controllers 13B and 14B of system B are K/2.
In the case of the conventional example of this type, feedback loops for the servo valves 81 and 82 can be formed individually for system A and system B. Accordingly, the lengths of fluid flow paths in system A and system B can be made equal. However, it is difficult to activate both of the systems strictly at the same time, and there has been a problem that force fighting caused by turning forces applied to end A and end B of the synchronous link 2 is not sufficiently eliminated.